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MIAMI (CBSMiami) – Homicide detectives pored over a modest home in Westchester Monday morning where a father and son were found shot to death.

Neighbor Ramona Gomez said a woman two doors down heard arguing, then gunfire and called police. The dead men are 85-year-old Rafael Alfonzo and his 56-year-old disabled son Rafael Junior. Police are tentatively calling it a murder suicide.

Gomez told to CBS4 News that, despite his age, Alfonzo Senior was active, often working in the yard of the house on S.W. 82nd Court. His son, wheelchair-bound, was rarely seen.

Gomez said the son appeared to be mentally and physically challenged. The doubly fatal shooting shook the neighborhood of retirees and working families.

“I walk my dog here every day,” said resident Sandra Frasser. “It’s amazing we have something like this happen. It’s unbelievable.”

A female relative came and left the home where the two victims lived alone, declining to speak with reporters.

While police are classifying the killings as a murder suicide, pending further investigation, they have released no details.

They have not revealed who they believe shot whom, or why.